There aren't really many very relevant threads I can find referring to either of these
specific issues being discussed before. There are two of borderline relevance:
For fumbles:
http://www.bay12forums.com/smf/index.php?topic=28156For attacking yourself:
http://www.bay12forums.com/smf/index.php?topic=63250There have been some other failure threads, but related to failing to craft in fortress mode rather than an adventure mode focus. The previous fumbles thread relates to balance and stumbles, not wounding yourself due to an absolute dearth of weapon skill and spatial sense (check out the second post from Footkerchief quoting one of the old power goals). It is also from 2008.
The 'attacking yourself' thread is from last August, which is more recent but predates the November addition of aimed attacks. In fact a few posts from the thread state that with the addition of aimed attacks the ability to attack yourself could become more useful. I think given that aimed attacks have now been implemented and the interaction targeting framework is incoming, this might be a good time to quickly add self-targeting, if it is as simple as adding 'yourself' to the code for 'valid combat targets'.
Not being Toady I can't say whether this would be easy to implement, but if it is I think it's a reasonable suggestion for the next few releases. If it isn't easy, it could await more meaty combat rewrites. As a suggestion that doesn't seem to have been specifically addressed before.
With that said, while I have done multiple searches for each of these two ideas using varying keywords, it's always possible I missed a thread somewhere due to an obscure keyword being used or a simple brain fart on my part missing a common synonym. If so, feel free to throw me the link. I kept the first post short to avoid TL:DR and set the tone for this suggestion: something that would be nice to quickly throw in during the coming months, if it is trivial to implement.